The present invention relates to a heat exchanger, and particularly provides a heat exchanger adapted for use in hot water heaters, which is provided with a valve for control of the flow rate of a thermal medium fluid such as hot water.
In a conventional type hot water heater used in a motor vehicle for instance, a heat exchanger (heater core) is connected by means of a pipe with a water pump mounted on the engine of the vehicle. Hot water is pumped by the water pump and fed through the pipe from the engine to the heat exchanger. The hot water is then cooled by the heat exchanger and is returned to the water pump by way of another pipe.
A heat exchanger of this kind is disclosed e.g., in U.S. patent application Ser. No. 064,750, now U.S. Pat. No. 4,266,604, issued May 12, 1981, assigned to the assignee of the present application, in which two tanks, each composed of tank elements molded from a synthetic resin material and combined together, are joined to either side of a heat exchanger matrix which comprises hot water tubes and radiating fins.
According to conventional type heat exchangers of this kind including this disclosed type, usually a flow control valve is mounted in a hot water inlet pipe connected to the heat exchanger matrix at an inlet side thereof to control the flow rate of hot water being supplied to the heat exchanger. Such flow control valve is previously mounted in the pipe, and this pipe thus having the flow control valve mounted therein is connected to a tank on the inlet side of the heat exchanger matrix after the heat exchanger matrix and the tank are put together.
Therefore, the conventional exchangers require a measure for joining the hot water inlet pipe with the flow control valve mounted therein, to the tank of the heat exchanger. Further, a sealing means is also necessary for prevention of leakage of hot water through the junction of the pipe and the tank. The design of the junction of the tank and the hot water inlet pipe including the joining and sealing measures involves problems such as the increase of the number of the heat exchanger parts, complicated construction, increased size, and consequent increase in the manufacturing cost.
Furthermore, the flow control valve of the above-mentioned kind is constructed such that to secure sealing between the valve body and the valve seat, the valve body is urged against its valve seat by the force of a spring, as disclosed in Japanese Utility Model Publication No. 52-54020 for instance. This construction involves a problem of low operatibility. That is, not only the urging force of the spring but also the pressure of hot water in the hot water supply pipe acts upon the valve body, thus requiring a large operating force for actuating the valve body.